Luiz Bertelli

AIDE: internal dosimetry software.

AIDE (Activity and Internal Dose Estimates) is a software for calculating activities in compartments and committed doses due to occupational exposures, and for performing intake and dose estimates using bioassay data. It has been continuously developed and tested for more than 20 years. Its calculation core has been applied in several situations, like performing all dose estimates due to (137)Cs intakes, which occurred during the Goiania accident in 1987; performing quality assurance of the ICRP Task Group on Dose Calculations regarding calculations of activities in compartments and generation of dose coefficients for adults due to intakes by inhalation, ingestion and injection of several radionuclides; and producing the tables of activities in compartments and dose coefficients using the NCRP Wound Model for the NCRP report. It provides several capabilities like performing calculations using modified Human Respiratory Tract Model parameters for the mechanical transport, blood absorption and partitions of deposit in the AI region. The existing systemic models can also be modified or new ones can be entered. All estimate procedures are in accordance with the methods presented in the ICRP-78 Publication, in the IAEA Safety Reports Series no. 37 and in the IDEAS Project Guidelines 2006.

Studies of Cs Retention in the Human Body Related to Body Parameters and Prussian Blue Administration

Using the in-vivo monitoring data from the individuals that suffered internal contamination in the Goiânia accident, a preliminary study on the elimination of Cs from their body was conducted. It was concluded that elimination follows a first-order linear kinetic pattern, both with and without Prussian Blue treatment. Cesium half-lives for both sexes were shown to be influenced mainly by the weight of each individual. In general, Prussian Blue seems to reduce the half-life by 32%. At the time our study was conducted, patients who were under treatment with the drug were receiving 3 g d-1, 6 g d-1, or 10 g d-1 of the medication. Our results suggest that there is an optimum dosage for a certain weight range to achieve this reduction in half-life, but one would need more data to statistically prove this assumption.

Efficacy of Prussian blue on 137Cs decorporation therapy.

AbstractPrussian blue (PB) is an efficient drug for enhancing cesium elimination from the body. Literature data on the efficacy of PB treatment in dosages that vary from 1–10 g d−1 was reviewed. Cesium biokinetics was simulated using a detailed systemic biokinetic model. The same model was used to simulate the maximum action of PB by interrupting the enterohepatic circulation. Model results reproduced reasonably well the literature data on the efficacy of PB administered to humans after incidental cesium intakes, as well as results from animal experiments. Maximum efficiency of the reduction of the long-term half-time is obtained with the administration of 3 g d−1 PB to the adult. Maximum efficiency of reducing the Cs body burdens is obtained when PB is administered on the first day after the intake, due to the increase of the short-term elimination of cesium. The model predicts that reduction of the long-term half-life is not affected by the time after intake that PB is administered, as long as it is given within the interval from 1 h to 1 y after the intake.

UNCERTAINTIES IN INTERNAL DOSES CALCULATED FOR MAYAK WORKERS—A STUDY OF 63 CASES

This study makes use of 63 cases of Mayak workers exposed to Pu-239 with autopsy data and some late-time urine bioassay data. In addition, air-concentration data--used to construct monthly average values--are available for each case, which provide the time dependence and potential magnitudes of normal inhalation intakes for each case. The purpose of the study is to develop and test Bayesian methods of dose calculation for the Mayak workers. The first part of the study was to quantitatively characterise the uncertainties of the bioassay data. Then, starting with three different published biokinetic models, the data are fit by varying intake and model perturbation parameters, e.g., parameters influencing the lung, thoracic lymph nodes, liver and bone retention. Statistical self-consistency arguments are used to check the measurement uncertainty parameters within the Poisson-lognormal model. The second part of the study is to set up and test Bayesian dose calculations, which use the point determinations of biokinetic parameters from the study cases within a discrete, empirical Bayes approximation. The main conclusion of the study is that these methods are now ready to be applied to the entire Mayak worker population.

Determination of 99Mo contamination in a nuclear medicine patient submitted to a diagnostic procedure with 99mTc

99mTc is a radionuclide widely used for imaging diagnosis in nuclear medicine. In Brazil it is obtained by elution from 99Mo-99mTc generators supplied by the Nuclear Energy Research Institute (IPEN). The elution is carried out in radiopharmacy laboratories located in hospitals and clinics. Depending of the quality of the generator and conditions of use during the elution process, 99Mo can be extracted from the column of the generator, becoming a radionuclidic impurity of the eluate used for the obtention of the radiopharmaceutical to be administered to the patient. 99Mo emits high-energy photons and beta particles and its presence degrades the quality of the image and unnecessarily increases the radiation dose delivered to the patient. An in-vivo measurement technique was developed to verify the occurrence of internal contamination by 99Mo in nuclear medicine patients. Direct measurements were made in a volunteer who underwent myocardial scintigraphy with 99mTc-sestamibi. The results indicated the presence of internal contamination of the patien by 99Mot. The activity was tracked for several days, and an assessment of the radiation dose from the contaminant 99Mo was made.

Application of in-vitro bioassay for 137Cs during the emergency phase of the Goiânia accident.

In the Goiânia accident, many individuals suffered external and internal contamination. The screening of internal contamination was done through 137Cs urinary excretion. During the first month after the accident, only in-vitro bioassay procedures were done. Incorporation into the body and committed doses were estimated using age-specific mathematical models correlating these quantities to the 137Cs excreted in urine. The ratio of feces to urine of 137Cs excretion was used to evaluate the effectiveness of the administration of Prussian Blue on removal of 137Cs from the body.

Software for empirical building of biokinetic models for normal and decorporation-affected data.

Abstract This paper describes software (“RATDOSE”) developed to analyze data from animal experiments investigating the efficacy of chelating agents. An empirical model building approach is used where, starting from the simplest model structures, one minimizes &khgr;2 by varying transfer rates in the model. Model complexity is increased as needed until the minimum attained value of &khgr;2 per data point decreases to about 1. This approach requires careful treatment of data uncertainties and independent checks of data self-consistency. The biokinetic models can include second-order kinetics to describe the chelation chemical reaction. The radiation dose to the animal is also calculated using S quantities specific for the animal, although the tissue weighting factors used to calculate the effective dose are those for the human.

Emergency Department Management of Patients Internally Contaminated with Radioactive Material

After a radiation emergency that involves the dispersal of radioactive material, patients can become externally and internally contaminated with 1 or more radionuclides. Internal contamination can lead to the delivery of harmful ionizing radiation doses to various organs and tissues or the whole body. The clinical consequences can range from acute radiation syndrome to the long-term development of cancer. Estimating the amount of radioactive material absorbed into the body can guide the management of patients. Treatment includes, in addition to supportive care and long term monitoring, certain medical countermeasures like Prussian blue, calcium diethylenetriamine pentaacetic acid (DTPA) and zinc DTPA.

Three plutonium chelation cases at Los Alamos National Laboratory.

Chelation treatments with dosages of 1 g of either Ca-DTPA (Trisodium calcium diethylenetriaminepentaacetate) or Zn-DTPA (Trisodium zinc diethylenetriaminepentaacetate) were undertaken at Los Alamos Occupational Medicine in three recent cases of wounds contaminated with metallic forms of 239Pu. All cases were finger punctures, and each chelation injection contained the same dosage of DTPA. One subject was treated only once, while the other two received multiple injections. Additional measurements of wound, urine, and excised tissues were taken for one of the cases. These additional measurements served to improve the estimate of the efficacy of the chelation treatment. The efficacy of the chelation treatments was compared for the three cases. Results were interpreted using models, and useful heuristics for estimating the intake amount and final committed doses were presented. In spite of significant differences in the treatments and in the estimated intake amounts and doses amongst the three cases, a difference of four orders of magnitude was observed between the highest excretion data point and the values observed at about 100 d for all cases. Differences between efficacies of Zn-DTPA and Ca-DTPA could not be observed in this study. An efficacy factor of about 50 was observed for a chelation treatment, which was administered at about 1.5 y after the incident, though the corresponding averted dose was very small (LA-UR 09-02934).

An empirical multivariate log-normal distribution representing uncertainty of biokinetic parameters for 137Cs

A simplified biokinetic model for (137)Cs has six parameters representing transfer of material to and from various compartments. Using a Bayesian analysis, the joint probability distribution of these six parameters is determined empirically for two cases with quite a lot of bioassay data. The distribution is found to be a multivariate log-normal. Correlations between different parameters are obtained. The method utilises a fairly large number of pre-determined forward biokinetic calculations, whose results are stored in interpolation tables. Four different methods to sample the multidimensional parameter space with a limited number of samples are investigated: random, stratified, Latin Hypercube sampling with a uniform distribution of parameters and importance sampling using a lognormal distribution that approximates the posterior distribution. The importance sampling method gives much smaller sampling uncertainty. No sampling method-dependent differences are perceptible for the uniform distribution methods.